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At least 721 records · Page 40
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NASA NTRS1980

In situ exhaust cloud measurements

Airborne in situ exhaust cloud measurements were conducted to obtain definitions of cloud particle size range, Cl2 content, and HCl partitioning. Particle size distribution data and Cl2 measurements were made during the May, August, and September 1977 Titan launches. The measurements of three basic effluents - HCl, NO sub X, and particles - against minutes after launch are plotted. The maximum observed HCl concentration to the maximum Cl2 concentration are compared and the ratios of the Cl2 to the HCl is calculated.

Wornom, D.↗
NASA NTRS1979

A sensitivity analysis of volcanic aerosol dispersion in the stratosphere

A computer sensitivity analysis was performed to determine the uncertainties involved in the calculation of volcanic aerosol dispersion in the stratosphere using a 2 dimensional model. The Fuego volcanic event of 1974 was used. Aerosol dispersion processes that were included are: transport, sedimentation, gas phase sulfur chemistry, and aerosol growth. Calculated uncertainties are established from variations in the stratospheric aerosol layer decay times at 37 latitude for each dispersion process. Model profiles are also compared with lidar measurements. Results of the computer study are quite sensitive (factor of 2) to the assumed volcanic aerosol source function and the large variations in the parameterized transport between 15 and 20 km at subtropical latitudes. Sedimentation effects are uncertain by up to a factor of 1.5 because of the lack of aerosol size distribution data. The aerosol chemistry and growth, assuming that the stated mechanisms are correct, are essentially complete in several months after the eruption and cannot explain the differences between measured and modeled results.

Butler, C. F.↗
NASA NTRS1980

Examples of realistic aerosol particles collected in a cascade impactor

In this paper some scanning electron microscope photomicrographs showing examples of a variety of particulate aerosol shapes are presented. Compositions of particles also are presented. These particles represent samples from a number of different sources and locations including: solid propellant rocket motor plumes, active volcano plumes, the lower stratosphere over Sondrestrom, Greenland, and the upper troposphere over northern Texas. The particles were collected from aboard an aircraft with a cascade impactor which classified them according to aerodynamic size into 10 size intervals ranging from submicron to greater than 25 micrometers in diameter. The cascade impactor also served to measure the mass concentration as a function of particle size. The variety of shapes and compositions found among these particles suggest difficulties in obtaining reliable size distribution data from light scattering measurements.

Woods, D. C.↗
NASA NTRS1980

Fundamental studies in geodynamics

Progress in modeling instantaneous plate kinematics is reviewed, with emphasis on recently developed models of present day plate motions derived by the systematic inversion of globally distributed data sets. Rivera plate motions, the Caribbean South American boundary, Indian plate deformation, Pacific-North America, seismicity and subduction processes, and the study of slow earthquakes and free oscillations are discussed.

Anderson, D. L.↗
NASA NTRS1980

Overview of the Magsat program

The Magsat project which is designed to provide precise measurements of the near-earth geomagnetic field is examined. Rapidly obtained global surveys are possible through satellite observations without the long-term variations obtained by conventional surface measurements. The altitude for Magsat measurements is a trade-off between the lowest possible altitude necessary for increasing the anomaly signals and their spatial resolution, and the minimum satellite lifetime necessary for obtaining adequate data distribution. A nominal perigee of 350 km was selected. The background leading to the project inception and mission objectives are discussed along with plans to study regional geology and geophysics.

Ousley, G. W.↗
NASA NTRS1981

Training site statistics from Landsat and Seasat satellite imagery registered to a common map base

Landsat and Seasat satellite imagery and training site boundary coordinates were registered to a common Universal Transverse Mercator map base in the Newport Beach area of Orange County, California. The purpose was to establish a spatially-registered, multi-sensor data base which would test the use of Seasat synthetic aperture radar imagery to improve spectral separability of channels used for land use classification of an urban area. Digital image processing techniques originally developed for the digital mosaics of the California Desert and the State of Arizona were adapted to spatially register multispectral and radar data. Techniques included control point selection from imagery and USGS topographic quadrangle maps, control point cataloguing with the Image Based Information System, and spatial and spectral rectifications of the imagery. The radar imagery was pre-processed to reduce its tendency toward uniform data distributions, so that training site statistics for selected Landsat and pre-processed Seasat imagery indicated good spectral separation between channels.

Clark, J.↗
NASA NTRS1981

Avionics test bed development plan

A development plan for a proposed avionics test bed facility for the early investigation and evaluation of new concepts for the control of large space structures, orbiter attached flex body experiments, and orbiter enhancements is presented. A distributed data processing facility that utilizes the current laboratory resources for the test bed development is outlined. Future studies required for implementation, the management system for project control, and the baseline system configuration are defined. A background analysis of the specific hardware system for the preliminary baseline avionics test bed system is included.

Harris, L. H.↗
NASA NTRS1981

Avionics test bed development plan

The plan is for a facility for the early investigation and evaluation of new concepts for the control of large space structures, orbiter attached flex body experiments, and orbiter enhancements. This plan outlines a distributed data processing facility that will utilize the current JSC laboratory resources for the test bed development. The future studies required for implementation, the management system for project control, and the baseline system configuration are described.

Harris, L. H.↗
NASA NTRS1981

Antarctic meteorite newsletter. Volume 4: Number 1, February 1981: Antarctic meteorite descriptions, 1976, 1977, 1978, 1979

This issue of the Newsletter is essentially a catalog of all antarctic meteorites in the collections of the Johnson Space Center Curation Facility and the Smithsonian except for 288 pebbles now being classed. It includes listings of all previously distributed data sheets plus a number of new ones for 1979. Indexes of samples include meteorite name/number, classification, and weathering category. Separate indexes list type 3 and 4 chondrites, all irons, all achondrites, and all carbonaceous chondrites.

Stone, R.↗
NASA NTRS1981

Distribution of hot stars and hydrogen in the Large Magellanic Cloud

Far-UV brightness distribution data for the face of the Large Magellanic Cloud (LMC) are derived from calibrated electrographic imagery in the 1050-1600 and 1250-1600 A ranges, and far-UV fluxes for individual hot-star groupings in the LMC are compared with H-alpha measurements and with a 21-cm survey. It is found that large clouds of interstellar hydrogen contain smaller concentrations revealed by H-alpha emission and other clear regions where hot O-B stars excite no H II regions. Either (1) four of these associations lie behind the large interstellar clouds, or (2) the clouds may be very diffuse and extended in the line of sight. Six other peaks in far-UV flux not previously cataloged are also indicated.

Page, T.↗
NASA NTRS1982

Reconstruction of atmospheric pollutant concentrations from remote sensing data - An application of distributed parameter observer theory

The reconstruction of a concentration distribution from spatially averaged and noise-corrupted data is a central problem in processing atmospheric remote sensing data. Distributed parameter observer theory is used to develop reconstructibility conditions for distributed parameter systems having measurements typical of those in remote sensing. The relation of the reconstructibility condition to the stability of the distributed parameter observer is demonstrated. The theory is applied to a variety of remote sensing situations, and it is found that those in which concentrations are measured as a function of altitude satisfy the conditions of distributed state reconstructibility.

Koda, M.↗
NASA NTRS1982

Ejecta distribution around a small lunar crater

The ejecta deposit surrounding a one-half kilometer lunar crater was examined in search of a pattern to its distribution. Data reduction methods are described. Size and range frequency plots for the ejecta were generated.

Wetzel, S. J.↗
NASA NTRS1983

CNPQ/INPE LANDSAT system

The current status of the Brazilian LANDSAT facilities is described and main accomplishments are outlined. Receiving, recording, and processing substations and data distribution centers are discussed. Examples of the preliminary TM product produced by the Brazilian station are given.

Parada, N. D. J.↗
NASA NTRS1983

A function space approach to state and model error estimation for elliptic systems

An approach is advanced for the concurrent estimation of the state and of the model errors of a system described by elliptic equations. The estimates are obtained by a deterministic least-squares approach that seeks to minimize a quadratic functional of the model errors, or equivalently, to find the vector of smallest norm subject to linear constraints in a suitably defined function space. The minimum norm solution can be obtained by solving either a Fredholm integral equation of the second kind for the case with continuously distributed data or a related matrix equation for the problem with discretely located measurements. Solution of either one of these equations is obtained in a batch-processing mode in which all of the data is processed simultaneously or, in certain restricted geometries, in a spatially scanning mode in which the data is processed recursively. After the methods for computation of the optimal estimates are developed, an analysis of the second-order statistics of the estimates and of the corresponding estimation error is conducted. Based on this analysis, explicit expressions for the mean-square estimation error associated with both the state and model error estimates are then developed.

Rodriguez, G.↗
NASA NTRS1983

The Galileo spacecraft system design

The Galileo Orbiter differs markedly from its Mariner, Viking and Voyager predecessors in many aspects of its design, as dictated by its unique mission characteristics. Novel design features include a dual spin configuration, long life bipropellant propulsion, radioisotope thermoelectric generators, and a star scanner. Other major changes are related to Space Shuttle Orbiter compatibility. The selection of a distributed data system employing a high speed data bus represents a major advance over Voyager systems. The command, control and data handling functions for the Orbiter are merged into a single software-controlled subsystem. The paramount importance of software development in the design of Galileo subsystems is noted, in view of the requirement for total engineering and science data acquisition process reprogrammability.

Jones, C. P.↗
NASA NTRS1983

Mariner Mark II and the exploration of the solar system

NASA's Solar System Exploration Committee has proposed the Mariner Mark II concept for the next generation of deep-space planetary observation missions, which will yield Voyager- and Galileo-quality focused data sets at a fraction of the costs associated with those spacecraft. Cost-limiting strategies under consideration include the use of reconfigurable designs, a multimission ground support system, and the incorporation of such selected new technologies as an all-X band telemetry system, fiber-optic rate sensors for use as an inertial reference system, image compression, and electronic and optical disk data distribution. It is believed possible to meet cost goals of 150-300 million/mission. The missions under consideration are comet rendezvous and sample return, main belt asteroid flybys, and orbits, flybys and probes of Saturn, Titan, Neptune and Uranus.

Neugebauer, M.↗
NASA NTRS1983

The IRAS project organisation and mission operations

The project organisation of IRAS is described, showing the tasks assigned to each project group during post-launch operations. The satellite is described, emphasizing the detectors. In the task division, the role of the U.S. is to construct the telescope and survey instrument, launch the satellite, process final science data for the survey instrument, and provide certain standard satellite items. The Netherlands construct the spacecraft and three additional instruments, integrates and tests the overall satellite, and designs and participates in the development of the operational system. The U.K. provides the operational control center and primary tracking station, generates a system for preliminary science analysis of the survey data, provides housekeeping analysis software and science data distribution software, and staffs the control center operations. The teams involved in mission planning and operations, and their roles, are identified, and a block diagram of the operations organisation is presented.

Van Holtz, R. C.↗
NASA NTRS1983

CNPq/INPE LANDSAT system

The status of the Brazilian LANDSAT facilities and the results achieved are discussed. The receiving and recording systems, processing laboratories and products, and data distribution are addressed.

Parada, N. D. J.↗